Implantable medical systems, for example, those providing electrical stimulation for cardiac or neurological therapy, often include a pulse generator device and an elongate medical electrical lead that extends from the device to a stimulation site in a body of a patient. Numerous configurations of implantable medical electrical lead connectors have been disclosed over the years, many of which are directed toward compliance with international industry standards; these standards specify essential dimensions and performance requirements to assure compatibility of connection between pulse generator device connector receptacles and lead connectors among a variety of manufacturers. One such standard dictates the form for a four-pole in-line connector of cardiac pacing and defibrillation leads and is commonly known as the IS-4, or in some cases, the DF-4 standard.
FIG. 1 is a schematic with a corresponding chart that describes various configurations of an exemplary implantable medical electrical lead 100. Lead 100 includes a connector 120 in conformance with the aforementioned IS-4 standard. FIG. 1 illustrates connector 120 including a terminal connector pin 110, three contact surfaces cs1, cs2, cs3, and four sealing surfaces ss1, ss2, ss3, and ss4, wherein, according to the IS-4 standard, pin 110 and first contact surface cs1 are low voltage contacts, and second and third contact surfaces cs2, cs3 are high voltage contacts. The IS-4 standard also requires a specific configuration of terminal connector pin 110 and a uniform outer diameter D of connector 120. Those skilled in the art understand that pin 110 and contact surfaces cs1-cs3 are configured to mate with device contacts mounted within a connector receptacle of the device, and sealing surfaces ss1-ss4 are configured to mate with sealing rings, which are interspersed between the contacts within the device connector receptacle, so that an electrical coupling is made between each device contact and the corresponding pin/contact surface, within the receptacle, and these couplings are electrically isolated from one another by the sealing rings.
FIG. 1 further illustrates lead 100 including an elongate body 130, which extends distally from connector 120 to a low voltage distal-most electrode de, two types of which are shown: one for what is known as a passive fixation lead (designated ‘P’), and the other for what is known as an active fixation lead (designated ‘A’). Although not shown, those skilled in the art understand that lead body 130 includes an elongate conductor extending therein, which couples distal-most electrode de, of either type of lead 100, to terminal connector pin 110, wherein, if lead 100 is the active fixation type A, rotation of pin 110 is translated, via the conductor, to electrode de, which is formed as a helix for fixation in tissue at a target implant site. If lead 100 is the passive fixation type P, electrode de may be held at the target implant site via tines 135. Each type of lead 100 may further include one or more of electrodes e1, e2, e3, which are shown mounted around lead body 130, wherein body 130 further includes a corresponding one or more elongate conductors (not shown), for example, to couple electrode e1 to contact surface cs1, to couple electrode e2 to contact surface cs2, and to couple electrode e3 to contact surface cs3. It should be noted that lead body 130 further includes insulative tubing that isolates the elongate conductors from one another. Various suitable configurations and constructions for each of electrodes de, e1-e3 are well known to those skilled in the art.
Either type of lead 100 may be configured according to any of the four exemplary configurations outlined in the chart of FIG. 1. In the first configuration, lead 100 includes just electrodes de and e1, wherein e1 is employed for pacing and sensing, in combination with electrode de, and for defibrillation, in which case electrode e1 is coupled to both first and second contact surfaces cs1, cs2 of connector 120. In the second configuration, lead 100 includes electrodes de, e1, and e3, wherein electrodes de and e1 function the same as in the first configuration, and electrode e3 is also employed for defibrillation, being coupled to contact surface cs3. In the third configuration, lead 100 again includes electrodes de, e1, and e2, but electrode e1 is only employed for pacing and sensing, so is not coupled to contact surface cs2, instead electrode e2 is coupled to contact surface cs2. In the fourth configuration, lead 100 includes all of the illustrated electrodes de, e1-e3, wherein e1 is solely employed for pacing and sensing, and electrodes e2 and e3 are solely employed for defibrillation.
Although only the fourth configuration employs all of electrodes e1-e3, the aforementioned IS-4 industry standard requires the presence of all contact surfaces cs1-cs3 and all sealing surfaces ss1-ss4 for the other three configurations, even though contact surface cs3 may be inactive, to preserve the standard form of connector 120. Furthermore, it should be noted that the IS-4 industry standard also applies to low voltage only lead connectors, which have the same form as connector 120, but contact surfaces cs-2 and cs3 are designated for low voltage electrodes. Thus, a modular assembly for lead connector 120 is desirable, to increase the flexibility in manufacturing a variety of implantable medical electrical lead configurations, of both the active fixation type A and passive fixation type P. Even though some constructions of lead connectors that incorporate modular assemblies, are known in the art, there is still a need for new constructions and manufacturing methods.